Floor coating compositions (e.g., polishes) are applied to flooring substrates, such as vinyl, tile or wood, to maintain a clean and sanitary appearance. They are generally intended to be sacrificial coatings which form a film that protects the underlying flooring substrate by sacrificially accepting and resisting marks, soils, scuffs, abrasion, and scratches encountered during normal use of the substrate. During its service life, the protective films must withstand rigorous maintenance practices such as aqueous detergent scrubbings and abrasive mechanical abrasion to remove, when possible, the soils, scuffs and scratches accumulated with time. When the useful or aesthetic life of the protective film has expired, it is removed from the substrate and replaced with a new coating composition. Thus, easy removability is just as important as the coating's ability to resist marks, soil, scratches, and detergents.
Past technology employed transition metal cross-linking, such as with zinc, to strike a balance between detergent resistance and removability, while maintaining the durability of the coating composition. More recently, heightened concerns regarding environmental safety have made use of zinc cross-linking technology in floor polish compositions less acceptable. Zinc can be toxic to aquatic life in streams, rivers, and lakes. Municipal sewer facilities have threshold limits on the level of zinc that enters their facilities in the waste water. Although the floor-finish industry's contribution to total zinc input may be relatively small, it remains a focus of the municipal sewer authorities. Many United States municipalities and school districts, as well as the United States Green Building Council, have begun to require the use of zinc free finishes in their custodial cleaning products and service contracts.
Zinc-free floor polish compositions developed to date tended to fall short of the expected performance characteristics by either not providing sufficient resistance to repel scuffs, soils, and scratches, or by failing to provide acceptable resistance to the detergents and mechanical rubbing employed to restore the coatings. For example, see U.S. Patent Application Publication No. 2007/0254108 which discloses floor coating compositions using calcium instead of zinc but which fail to meet industry requirements. Also, see U.S. Pat. No. 6,586,516 which discloses aqueous coating compositions comprising acetoacetate functional polymers and a divalent metal ion which may be zinc, but which is preferrably an alkaline earth metal ion, such as calcium, magnesium, or mixtures thereof. The compositions of U.S. Pat. No. 6,586,516 provide surface coatings having scuff mark resistance mar resistance and impact resistance for a variety of substrates. End-use customers would strongly prefer zinc free floor polishes that provide the performance that has come to be expected from current zinc-containing state-of-the-art floor finishes, including resistance to scuffing, marring, marking, soiling, etc. and also providing favorable removability properties.
The problem encountered when multivalent metals other than zinc, such as calcium or magnesium, are used to achieve crosslinking in floor coating compositions is that higher levels of such other metals must be used, while concurrent coating stability becomes difficult to maintain. It is also desired to incorporate other metals such as aluminum, zirconium and titanium which normally cannot be done using traditional complexing monomers (e.g., acrylic acid, methacrylic acid, itaconic acid).
Other solutions have been attempted as well. For instance, U.S. Pat. No. 5,574,090 describes an alternative to metal crosslinking in aqueous coatings systems in which a coating composition comprises a combination of a swellable polymer with a polymer which contains functionality that will interact with the swellant to facilitate stripping and removal of the coating at the end of its useful life. This patent further teaches that acid-functional polymers may be used with amine swellants and amine functional polymers may be used with acid swellants. U.S. Pat. No. 5,574,090 teaches that most preferred are polymers that contain carboxylic acid functional groups as the swellable polymers, in combination with amines such as ammonia and lower alkyl, or lower alkanol amines.
U.S. Pat. No. 5,426,142 teaches film-forming polymers which contain acetoacetate functionality and are further reacted with amino functional silane to produce self-crosslinking, ambient curing, film-forming polymers suitable for various uses including coatings and sealants for wood, glass and concrete.
More recently, it has been recognized that acrylic polymers having chelating functionality are useful for binding metal ions in various applications. For instance, U.S. Pat. No. 3,331,773 teaches preparation of water soluble polymers having chelating functionality which are useful as water treatment agents for inhibiting calcium and magnesium scale formation. These polymers are formed by grafting water soluble chelating monomers onto water soluble polymers having aliphatic polymeric backbones. Diethylenetriamine, ethylenediamine tetraacetic acid (EDTA), and other polyalkylene polyamine polyacetic acids are identified in U.S. Pat. No. 3,331,773 as examples suitable chelating monomers.
Additionally, U.S. Pat. No. 5,514,732 also describes contact lenses made from water insoluble polymers having chelating functionality. The polymers are made from aminopolycarboxylic acids with a polymerizable olefinic group, as well as a hydrophilic monomer and one or more crosslinking monomers.
U.S. Patent Application No. 2008/00262192 describes water-soluble polymers having a high chelating performance and clay dispersancy that are suitable for use as detergents, water treatment agents and dispersants. These polymers are made by polymerizing an amino group-containing allyl monomer derived from adding an amine compound, such as iminodiacetic acid (IDA), to an allyl monomer, such as allyl glycidal ether (AGE), with other polymerizable monomers including, without limitation, unsaturated monocarboxylic acid monomers.
Most recently, vinyl aminocarboxylate monomers have been found useful for providing amine-based chelating functionality. Vinyl aminocarboxylate monomers are an entire class of polymerizable acrylic monomers having amine-based chelating functionality and which are polymerizable along with ethylenically unsaturated monomers typically used to produce various types of acrylic monomers. This is related to the technology described in the aforementioned U.S. Patent Application No. 2008/00262192 where an AGE-IDA vinyl aminocarboxylate monomer is described and incorporated into carboxylic acid-based copolymers. Polymers comprising polymerized units derived from such vinyl aminocarboxylate monomers have been identified as effective chelating agents and, therefore, are expected to be useful in various possible applications. The present invention addresses the need for zinc-free floor coating compositions that provide excellent resistance to marks, soil, scratches, scuffs and detergents, while also providing superior removability characteristics for facilitating stripping at the end of the useful life of the coating. These floor coating compositions contain polymers having amine-based chelating functionality and are capable of binding metals at high loading levels to serve as an alternative to zinc-based crosslinking schemes for curing protective films.